Cottonique
The reference direct-skin brand: non-elastic, synthetic-free, formaldehyde-free, dye-free, bleach-free GOTS organic cotton, thread and all. The Nothing But Cotton line is the strict pass.
Filter carefully; not everything on the site is the Nothing But Cotton standard.
A US source in the The Second Skin directory. Check that it ships to Europe; where it does not, the directory lists a European alternative alongside it.